This is part of the Somerset House Film 4 Summer season from August 6th to 19th which is already proving very popular. A number of screenings have sold out but you can get details here and keep checking for returns. Tonight's event is part of a double-bill with An American Werewolf in London.
Time Out review:
That rare thing: an intelligent, beautifully acted, and gloriously funny British comedy. At the butt-end of the '60s, two 'resting' young thesps - Withnail (Grant, a revelation), a cadaverous upper middle class burning-out case with an acid wit and soleless shoes, and the seemingly innocent unnamed 'I' (McGann) - live on a diet of booze, pills, and fags in their cancerous Camden flat, until a cold comfort Lakeland cottage is offered for their use. For all its '60s arcana, this is no mere semi-autobiographical nostalgia trip, but an affecting and open-eyed rites-of-passage movie. Robinson's debut as writer/director (he scripted The Killing Fields) exhibits the value of the old virtues: characterisation, detail, and engagement. His characters are oddball, degenerate even, but rounded - none more so than the elephantine figure of Griffiths as Withnail's gay uncle Monty. Beautifully scripted, indecent, honest, and truthful, it's a true original.
Here (and above) is the trailer.